THE STUDY OF ORGANS. 37 



cording as to^wliether the food is, or is not, of a bind 

 that requires long digestion in the intestines ; in man 

 and other mammalia it is slung in its place by deli- 

 cate transparent membranes, called mesenteries. 

 •Between these two regions lie two large glands,^ the 

 pancreas and the liver, which communicate with 

 the alimentary canal each by a tube, called its duct. 

 The cells of the pancreas secrete a fluid called pan- 

 creatic juice, which is alkaline in reaction. Its 

 use is to complete the digestion of the starchy foods, 

 and also of any proteid food that the stomach has not 

 already disposed of. 



The Liver secretes and pours into the intestine 

 the substance called bile, which is also alkaline. This 

 substance aids the digestion of fats. It may be de- 

 scribed as a by-product of the animal economy; for 

 there la room to believe that the liver manufactures the 

 bile out of the waste and worn-out portions of the 

 blood. One of the chief reasons for thinkins' so is, 

 that one of the colouring matters of the bile is identi- 



' Glands are organs consisting of numbers of cells wliioli 

 have the work of secreting (separating or hiding away a store ; 

 Lat. secretus, from secenw) from the blood some substance 

 which is of use to tlie body, snch as gastric juice, mucus, bile, 

 etc. The name gland (Lat. glans, a nut or acorn) was given 

 them because the glands first noticed by anatomists were 

 organs that consist of a small hard round mass like a nut. 

 Hence', a layer or mass of secreting cells is called glandular 

 tissue, and a single secreting cell a glandular cell. The 

 appearance of such cells under the microscope is peculiar 

 and easily recognized. 



